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Bay Blog: Potomac River basin


Clean Air Act improves water quality in Chesapeake Bay

Air quality improvements throughout the Potomac River watershed—due primarily to the Clean Air Act—have helped improve water quality in the Chesapeake Bay, according to research from the University of Maryland Center for Environmental Science (UMCES).

When cars, power plants and other sources emit air pollution, it can be carried by wind and weather over long distances until it falls onto land or directly into the water. In fact, scientists estimate that one third of the nitrogen in the Chesapeake Bay comes from the air—through a process known as atmospheric deposition. And while studying water quality trends in the Upper Potomac River Basin, UMCES scientists confirmed that reductions in atmospheric nitrogen deposition are playing a large role in improvements in the area’s water quality.

“Most best management practices—like a riparian buffer or retention pond—only impact a relatively small area,” said Keith Eshleman, professor at UMCES’ Appalachian Laboratory and co-author of the study. “You can think about the Clean Air Act as a best management practice that affects every square meter of the watershed.”

Experts at the Chesapeake Bay Program will be able to incorporate the findings into their modeling efforts, in order to better simulate the benefits of the Clean Air Act on reducing nitrogen pollution. The study—along with other research, monitoring and data collected over the past decade—will support Bay Program decision-making during the upcoming Midpoint Assessment of the Chesapeake Bay Total Maximum Daily Load, or TMDL.

Last year, the Chesapeake Bay Program released an interactive story map illustrating how Clean Air Act regulations, as well as decades of enforcement actions, led to a steady decline in air pollution across the Chesapeake Bay watershed.

The study—“Declining nitrate-N yields in the Upper Potomac River Basin: What is really driving progress under the Chesapeake Bay restoration?”—can be found online.


Intersex fish widespread in Potomac River basin

The prevalence of intersex fish in the Potomac River basin has raised concerns about river health.

Intersex conditions, the presence of both male and female characteristics in an animal that should exhibit the characteristics of just one sex in its lifetime, occur when chemicals like pesticides, pharmaceuticals or personal care products enter the water and disturb the hormonal systems of fish and other species. Because the hormonal systems of fish are similar to those of humans, anomalies found in fish are an indication these chemicals may also pose a risk to people.

Image courtesy August Rode/Flickr.

According to a report released by the U.S. Geological Survey (USGS), intersex conditions in male smallmouth bass are widespread in the Potomac River basin: 50 to 75 percent of male smallmouth bass collected in the South Branch Potomac River exhibited signs of feminization, as did 100 percent of those collected at sites in the Shenandoah.

In the case of male smallmouth bass, the "intersex condition" reveals itself in the presence of immature eggs in the testes and of a certain protein--vitellogenin, normally found only in egg-laying females--in the circulating blood. Both conditions indicate exposure to chemical contaminants, and can result in reduced reproductive success or, in the case of a shorter-lived species like the fathead minnow, population collapse.

Intersex conditions have been linked to sewage flow from wastewater treatment plants and to runoff from farmland and animal feeding operations.

A popular sport fish, the smallmouth bass experienced spring kills in the Potomac and James rivers. A number of smallmouth bass collected during this survey were also observed with skin lesions, leading researchers to believe the fish may be a sensitive indicator of watershed health.

The USGS and Chesapeake Bay Program partners will use these findings to better identify chemical contaminants and their sources, planning to develop toxic contaminant reduction outcomes by 2013.

Learn more about the hormonal disruption of fish in the Chesapeake Bay watershed.

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